Osmium composition



March'Z, 1943. A. R. DEVERE UX 2,312,324

.OSMIUM comrosmzon Filed April 21, 1941 INVENTOR. windy-ea) 2. @evereax. BY 5% 21/12; flzu z'elg m,

Patented Mar. I 2, 1943 UNITED STATES-PATENT OFFICE I OSMIUM coMrosIrioNAndrew R. Devereux, Chicago, 111., assignor to Goldsmith Bros. smelting& Refining Company, a corporation of West Virginia ApplicatlonApril 21,1941, Serial No. 389,638 4 Claims. (01.- vs-m) This invention relates toa composition consisting predominantly of osmium, in which the osmiumisin a felted acicular non-dendritic form;

The degree of smoothness to. which a metal surface may be polisheddepends upon the microscopic texture ofthe metal itself. This is paronabove 2900.F. and is completed by maintaining the product atapproximately 3100 F. for 2 hours. a

The structure of the resulting composition is illustrated in thedrawings, in which Figure 1 is a photolit'hograph of an area of thecomposition which has been magnified about 2,000 diameters; and Figure 2is a corresponding photolithograph which has been magnified about 500diameters. It will be observed in both photographs that the osmiumparticles are in the form of rods l0 which are felted or interlaced. Itwill be noted that even at a magnification as high as 2,000 diametersthere are no discrete regions of soft constituent perceptible.

The present. invention is not limited to the particular matrix heredescribed, nor to the para phase, thatperceptible isolated regions ofthe soft constituent are no longer perceptible.

'In Devereux and Pfanstiehl Patent No.

2,206,616 is described an osmium composition consisting predominantly ofosmium, in which the osmium is in the form of discrete particles, I

non-dendritic in arrangement and form. The product there described wasproduced by the heat treatment of pressed powder particles of osmium andother metals. The present-invention relates to an improvement thereonand more particularly to a product produced by heat treating acomposition in such manner as to render the osmium particles acicular inform and felted in arrangement.

By following the present process there is a tendency for the matrix todissolve a portion of the osmium, and for the osmium particles todissolve a portion of the matrix, undergoing in the process a veryconsiderable change in form and arrangement, without, however, becomingdendritic. During the change, the matrix, being smaller in quantity thanthe osmium, has a tendency to disappear, and the final product issubstantially free from isolated areas of the relatively soft matrixmaterial. On the other hand, the particles of the osmium-rich phasebecome rod-like or acicular in form, and interlaced or felted inarrangement.

The preferred alloy consists of approximately 85% osmium and 15%platinum. The product is prepared by intermixing osmium and platinumpowders in the correct proportion, pressing them together under heavypressure, and then sintering the resulting crude mass at a suitabletemperature in an inert atmosphere.

The transformation of the material is carried ticular proportions ofosmium-rich phase and matrix set forth in the specific example, so longas the osmium is predominant in proportion and the structure produced isthat herein set-forth. This is likewise true of the physical conditionsattending the processing, such as the pressure of compacting, thetemperature of sintering, etc.

For example the replacement of some of the platinum by small proportionsof rhodium has a tendency somewhat to coarsen the structure, althoughthe general crystal shape is preserved. The addition of tungsten on theother handhas a tendency to refine the structure by 'making the crystalsizes considerably smaller, although the general shape thereof ispreserved.

The use of the narrow heat treating range here specified, in combinationwith the compositions here given, likewise has a tendency to reduceporosity, the materials prepared in accordance with the presentinvention being essentially non porous.

As stated, the material herein described is of particular value for usein pen points, in connection with which the interlaced acioular massesof osmium-rich phase, held in the almost imperceptible body of matrix,produce long wear and a highly satisfactory writing surface.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom.

What I claim as new, and desire to secure by Letters Patent, is: v

1. An osmium alloy consisting predominantly of an osmium-rich phase inthe form of acicular crystals in interlaced arrangement held together bya matrix consisting essentially of platinum there being an osmium-richphase in the alloy in the form of interlaced acicular crystalsnondendritic in arrangement, and an osmium-lean phase of platinum matrixmetal characterized by the absence of isolated masses of matrix, thematrix phase holding together the osmium-rich phase.

3. An alloy as set forth in claim 2, in which the osmium content is 85%and the platinum is 15%.

4. An osmium alloy consisting entirely of platinum group metal exceptfor impurities which do not aflect the characteristics of the al- 10y,containing substantially 85% of osmium and the balance beingsubstantially platinum metal,

there being an osmium-rich phase in the alloy in the form of interlacedacicular crystals and an osmium-lean phase of platinum matrix metalcharacterized by absence of isolated masses of matrix, the matrix phaseholding together the osmium-rich phase.

ANDREW R. DEVEREUX.

